Getting back to it, I would say that there is a lot of love for Roger Russell's design. It is a classic, sounds great, and has that warm Mc sound. They made more than 15,000 of them and it went on to become the C27. The basic design was used in the MX112,MX113, MX114, and MX115. I would say that this preamp design has had the most impact on early McIntosh history than any other, and is a brilliant design and is very widely recognized.